Fire-resistant storage containers, also referred to as fire-resistant safes, are generally constructed with internal and external shells that encapsulate spaces filled with insulation material. The internal shells form inner surfaces of the safes, and the external shells form outer surfaces of the safes. Together, the internal and external shells form a shuttering for molding the insulation material in place within the shells. The insulation material is generally made of a mixture that solidifies in the mold but retains a large amount of water within the solidified mass of material.
The internal and external shells are often fabricated from steel sheets, but can also be made as integral double-walled shells that are blow molded from a resin material. Several patents commonly assigned herewith describe the double-walled shells, blow molding processes for making the double-walled shells, and apparatus specially designed for carrying out the blow molding processes. These patents include: U.S. Pat. Nos. 4,770,839 and 4,846,662 to Legge; U.S. Pat. No. 4,948,357 to Legge et al.; U.S. Pat. No. 4,805,290 to Brush, Jr., et al.; and U.S. Pat. Nos. 4,898,707 and 4,993,582 to Arp. All of these patents are hereby incorporated by reference. Separate double-walled shells of resin material are used to form a body of the safes having an opening for receiving contents and a closure (e.g., door, cover, drawer head) for closing the opening in the safe body. The respective double-walled resin shells of the safe body and the closure are both filled with insulation material. Although the resin material is combustible and the external shells of the safe body and the closure burn away in a fire, thereby exposing the insulation material, resin material between the body and the closure only partly melts away, leaving a seal around the opening between the body and the closure. The resin seal resists the conduction of heat and the passage of hot gases into the safes.
Several other advantages also accrue from use of resin material to form the internal and external shells of fire-resistant safes. For example, the resin shells provide a good vapor barrier to retard evaporation of water from the insulation material in both the safe body and the closure. Also, the resin material is lightweight, but resists abrasion and can be molded to a wide variety of shapes and textures.
However, when used as shutters for holding the insulation material in place while the insulation material cures and solidifies, the internal and external shells of resin material tend to bow apart, creating variations in the volume of insulation material required to fill the shells. Accordingly, it has been necessary to overfill the shells to prevent gaps from forming between the solidified insulation material and the resin shells.
Each of the double-walled shells of resin material is molded with a pair of funnels that are used to help fill the shells with the insulation material. Initially, the funnels are molded as closed projections but, thereafter, are cut open by a sawing operation at a predetermined height above the shells. One of the funnels (the larger of the two) guides insulation material into the shells. The other funnel allows air to escape from the shells while the shells are being filled. Air gaps between the insulation material and the resin shells are prevented by overfilling the shells so that the insulation material rises a considerable height (i.e., two centimeters or more) within the funnels.
The insulation material within the double-walled shells can be initially cured at elevated temperatures. This significantly reduces the total amount of time required to cure the insulation material. While curing, the double-walled shells of the safe body and the closure are braced together to maintain a tolerance for flatness of the respective external shells. The bracing is not removed until the insulation material is sufficiently cured to hold its desired shape.
After the insulation material has cured to a solid state, a second sawing operation is used to trim the funnels filled with insulation material to a limited height (i.e.. less than one centimeter) above the double-walled shells. Following this, holes are drilled through the resin shells and insulation material for attaching a latching mechanism, and other holes are drilled through the insulation material within the funnels for attaching escutcheon plates covering the latching mechanisms and the funnels.
The sawing and drilling operations through both the resin material and the solidified insulation material are especially difficult because of the different cutting characteristics of the two materials. Accordingly, it is not possible to use tooling that is especially suited for cutting either material. The operations are also messy and time consuming. In addition, speed nuts or other fasteners for anchoring the escutcheon plates are clearly visible against the internal shells.